Monday, March 11, 2013

Augmentation Cystoplasty (part 6)


Preoperative evaluation

Urine analysis, urine culture, and cytology (in adults) allow proper preoperative treatment of infection and investigation of potential occult malignancy. Sterile urine at the time of surgery is crucial in all patients, especially those with ventriculoperitoneal shunts.
Obtain a serum chemistry panel to rule out metabolic acidosis and to allow for assessment of renal failure with and without surgical therapy. Conduct a complete blood cell count to identify anemia or infection.
The kidneys and upper urinary tract should be imaged with renal ultrasonography to identify any upper tract anomalies and assess the renal parenchyma. In the presence of hydronephrosis, upper tract obstruction (eg, ureteropelvic junction obstruction) should be ruled out in addition to lower tract pathology.
Voiding cystourethrography should be performed to evaluate bladder size and contour, the presence of any diverticula, the anatomy of the bladder neck, and the presence of vesicoureteral reflux. This can also be performed as part of videourodynamic evaluation.
Assess urinary continence with a voiding diary and Valsalva leak point pressure.
Urodynamic evaluation should be performed if the patient has a history of dysfunctional voiding, though some surgeons perform this test in all patients in whom augmentation cystoplasty is being considered. Consider fluoroscopic video monitoring to assess for vesicoureteral reflux and to determine the bladder pressures at which reflux occurs.
Twenty-four–hour urine-volume assessment helps in planning the final reservoir size.
Cystoscopy, which can be performed immediately before augmentation cystoplasty under the same anesthesia, is useful for identifying occult urethral valves, strictures, or unsuspected bladder pathology.
Colonoscopy or barium enema may be considered in an older patient who has the potential for diverticular disease or colon cancer. This is even more important if the large intestine is the planned segment for augmentation cystoplasty.

Planning for concomitant procedures

Some patients who are candidates for augmentation cystoplasty also have ureteral reflux. Patients who have bladder exstrophy and who require augmentation cystoplasty should undergo simultaneous ureteral reimplantation. These patients have abnormal ureteral insertions to the bladder, and with bladder neck repair for continence, they often have elevated bladder pressures. Thus, tunneled reimplantation is almost universally performed, usually in a cephalad manner toward the bladder dome so as to follow the course of the ureter.
The role of ureteroneocystostomy in other patients is less clear. In patients with reflux at high bladder pressures, the augmentation procedure ideally resolves the issue. However, if low pressure causes reflux, the problem may persist after augmentation.
If a patient has grade 4 or 5 ureteral reflux at bladder-filling pressures lower than 40 cm H2 O, tunneled ureteral reimplantation into the native bladder tissue should be more strongly considered. Patients with low-grade reflux (ie, grade 1 or 2) at higher bladder pressures may undergo augmentation in the hope that the reflux will resolve with decreased bladder storage pressures.
A history of renal scarring, a history of pyelonephritis, the level of renal function, and the patient’s willingness to undergo future surgery should all be considered in counseling patients and parents and deciding whether to perform concomitant ureteral reimplantation at the time of augmentation cystoplasty.
In adult patients for whom a continent catheterizable stoma is planned, some surgeons routinely perform bladder-neck closure; however, if the outlet is intact and continent, it should be maintained to provide an alternative route for catheterization. Many surgeons feel that surveillance endoscopy is much easier in patients with an open bladder neck.
Associated urologic or gastrointestinal (GI) issues arising from congenital anomalies or acquired neurologic impairment may necessitate concomitant procedures. Urinary continence can be achieved with an artificial urinary sphincter (in males) or a urethral sling placement (in females). Construction of a continent catheterizable stoma assists with urinary emptying. A Malone antegrade catheterizable enema (MACE) procedure is used for neurogenic constipation.
In a small uncontrolled study, De et al discussed augmentation cystoplasty as an ancillary procedure to salvage prostatectomy after failed radiation therapy for localized prostate cancer; continence was improved, and 7 of 9 patients responding to a quality-of-life questionnaire stated that they would undergo the operation again.[15, 16] Because of the risk of high-bother urinary incontinence, the authors studied salvage prostatectomy with concomitant ileal augmentation, bladder neck closure, and creation of a catheterizable appendicovesicostomy.
In patients undergoing retropubic prostatectomy as primary treatment for prostate cancer who are at high risk for bladder dysfunction due to longstanding outlet obstruction, concomitant bladder augmentation is also an option.

Selection of tissue for augmentation cystoplasty

Proper selection of the optimal tissue for augmentation cystoplasty (see Table 1 below) begins with analysis of the patient’s anatomy and comorbidities but also requires consideration of intraoperative anatomic findings. One should always be prepared to use alternatives to the planned augmenting segment if the patient’s anatomy is unfavorable for the planned procedure.
Table 1. Comparison of Tissues for Augmentation Cystoplasty
Tissue Segment
Advantages
Disadvantages
Stomach
Decreases mucus, infection, and stones; better for short gut and acidosis/azotemia
Hemolytic dysuria syndrome
Jejunum
None (used only if other segments are contraindicated/unavailable)
Electrolyte disturbances; malabsorption
Ileum
Usually available, well-tolerated
Electrolyte disturbances; mucus
Large intestine
Usually available, well-tolerated
Electrolyte disturbances; mucus; sigmoid: strong contractions
Ureter
Minimizes mucus, infection, stones and electrolyte effects
Rarely available

Gastrocystoplasty may be considered in patients with renal insufficiency (creatinine level > 2 mg/dL) or significant metabolic acidosis. Using a gastric segment does not appear to worsen the acidosis and may preserve renal function. However, this procedure can be difficult to perform, it does not eliminate the risk of severe electrolyte abnormalities, and a significant number of these patients experience dysuria.
Patients who have a reduced amount of intestine (eg, anomalous short gut, previous intestinal removal, or cloacal exstrophy) may also be considered for augmentation cystoplasty with stomach rather than intestine. In patients with short gut or cloacal exstrophy, ileum is also commonly used for Mitrofanoff channel and augmentation, with GI consultation.
Ureterocystoplasty is a favorable option in patients with a massively dilated ureter; the use of ureteral tissue curbs the electrolyte imbalance and mucus production observed with intestinal segments. If the ipsilateral kidney is minimally functional, nephrectomy can be performed at the time of surgery.
With removal of the ileocecal valve, patients with neuropathic causes of bladder dysfunction (eg, spina bifida) may experience severe diarrhea that can cause fecal incontinence; thus, the combined use of distal ileum and cecum is discouraged in these patients.
In general, ileum and large intestine both handle well surgically and make excellent intestinal segments for augmentation. However, they both produce mucus and can have problematic peristalsis if not properly detubularized. Both types of augmentation segment have been well tested, and the choice of one over the other is largely a matter of individual surgical preference.
Some patients with neurogenic bowel dysfunction have a redundant sigmoid colon, which is therefore the segment of choice. In addition, this is the preferred segment in patients who do not require a continent catheterizable stoma.
Jejunal augmentation segments are rarely used, because of the importance of the jejunum in nutritional absorption and the severity of electrolyte abnormalities associated with the use of jejunal tissue.
If a patient or their caretaker is poorly compliant, an incontinent ileovesicostomy (ie, an ileal chimney with stoma) may be considered as a means of reducing the risk of perforation. This can be reversed when the patient can responsibly and independently manage the catheterization schedule.
Alternative tissue sources
Desai et al used ureteral tissue balloon expanders before laparoscopic bladder augmentation in a porcine model.[17] Basic science researchers continue to investigate potential alternatives to autologous tissues for augmentation cystoplasty. Small-intestine submucosa and synthetic polymeric substances are being studied. Tissue-engineering efforts continue, though reproducing the elastic and contractile properties of the bladder is challenging. Tissue engineering with nanostructured polymeric scaffolds appears promising.[18]
The use of any such surfaces could expand bladder volume and decrease bladder compliance without the morbidity and potential complications of intestinal harvesting. Potential benefits would include decreases in complications, operating time, metabolic derangements, and deleterious effects on bowel function.

Bowel preparation

All patients undergoing augmentation cystoplasty require preoperative mechanical and antibiotic bowel preparation.[19] Patients stay on a clear liquid diet for 2 days prior to the operation and take magnesium citrate the night before surgery.
Preoperative inpatient hospital admission should be planned for patients with renal insufficiency, chronic constipation, or a high risk of dehydration so that intestinal evacuation can be performed with concomitant monitoring and treatment of serum electrolytes and fluid status.
Scheduled oral erythromycin base and neomycin are often administered the night before surgery, and intravenous antibiotics are given 1 hour before the incision.

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